Electrical terminal connection, especially for connecting an outer conductior of a coaxial cable

ABSTRACT

The invention relates to an electrical terminal connection, especially for connecting an outer conductor of a coaxial cable, characterized by the following novel developments: the electrical terminal connection is embodied in a two-stage manner; the plug-in element comprises at least two plug-in sections which are staggered in the plug-in and axial direction, both the first plug-in section in the plug-in direction and the following plug-in section being provided with a knurl on the outer periphery thereof; the receiving opening comprises a first receiving section and a second receiving section which are staggered in the plug-in and axial direction of the plug-in element; and the cross-sectional size of the two plug-in sections and the two complementary receiving sections differs in that the radial dimension or outer dimension of the plug-in sections provided with the knurl is slightly larger than the radial or outer dimension of the receiving section respectively co-operating therewith.

The invention relates to an electrical terminal connection, especiallyfor connecting an outer conductor of a coaxial cable in accordance withthe preamble of claim 1.

Electrical terminal connections, especially for connecting an outerconductor of a coaxial cable, generally comprise a plug-in element whichcan be plugged into a socket or generally into a coupling having acorresponding plug accommodating opening.

Such coupling devices may also be formed, for example, on anelectrically conductive metal part, a plate, a wall, i.e. generally ahousing part or an electrically conductive housing, to which, forexample, it is intended to connect an electrical coaxial cable. Theinner conductor is insulated from the outer conductor and is in thiscase plugged into an inner conductor coupling part. The coaxial cableprovided with a corresponding outer conductor sleeve in this case makescontact with a sleeve-like part of the coupling device in order toproduce an electrical connection between the outer conductor of thecoaxial cable and the plug-in element and, by means of this, generallywith a housing or housing part.

When flexible coaxial cables are used which, as is known, are notcapable of absorbing high torques or radial forces, various problemsmay, however, result. Firstly, it is not possible to realize aforce-fitting connection between the outer conductor and, for example,an electrical housing without the use of additional parts.

On the basis of this, it has already been suggested, for example, in US2001/0053633 A1, to press a plug-in element into an accommodatingopening in a metallic wall. For this purpose, the end of a coaxialconductor generally has the insulation stripped from it in acorresponding manner, i.e. the insulation is also stripped from theouter conductor over a certain axial dimension, in order to position anadapter part there which is in the form of a metal sleeve. Thedistancing area between the inner wall of the sleeve-like adapter partand of the coaxial cable outer conductor is electrically connected bymeans of soldering. This adapter part is then pressed into a hole in aforce-fitting manner, said hole being formed, for example, in anelectrically conductive housing, housing part, an intermediate wall etc.The inner conductor may then protrude through the corresponding hole inthe housing wall part into the interior and be electrically connectedthere using conventional means.

If castings are used in the case of such press-in connections, press-insleeves having a corresponding outer knurl need to be used owing to hightolerances. In this case, the sleeves each have a radially protrudingand circumferential ring which, in the pressed-in position, rests on theouter side of the wall with which electrical contact is to be made or ofthe stop etc. Since this stop surface, however, can never lie evenly(owing to irregularities of the corresponding stop wall, themisalignment of the pressing-in die etc.), no clear, unique electricalcontact conditions can result which can always be reproduced, which isassociated with all of the disadvantages emanating therefrom. Inaddition, there is the risk of slackening owing to relaxation and owingto thermal cycling.

DE 73 35 171 U discloses a device for connecting an outer conductor andfor providing strain relief for a coaxial cable, it not being possibleto see clearly from the figures whether the plug-in element is onlyplugged or even pressed into an accommodating opening.

Finally, however, electrical connection devices are also known, inparticular for coaxial cables, in the case of which a contact bushing isplaced onto the coaxial cable at the plug end over a certain axiallength on an outer conductor region which has had the insulationstripped from it, said contact bushing in this case interacting with aunion nut so as to produce axial forces. The union nut may be screwedonto a corresponding threaded attachment, which is, for example, formedon the housing wall with which contact is to be made. However, since theunion nut may have a radial spacing, even if it is a minimum radialspacing, radially on the inside in the region in which the outerconductor sleeve of the coaxial cable is passed through, in this caselikewise undefined electrical contacts result.

DE 198 24 808 C1 discloses a holder for elongate bodies having anelectrical shield, said known holder having two accommodating sections,which lie offset with respect to one another and which have at least twoassociated plug-in sections which lie offset with respect to one anotherin the plug-in direction. The arrangement of the plug-in element in theaccommodating opening in this case takes place by means of the plug-inelement being pressed into the accommodating opening.

DE 20 22 318 B2 also discloses a tubular mounting element in the form ofan electrical terminal connection for the purpose of inserting andfixing components for radio interference suppression in a manner whichis resistant to high frequencies in shielding walls, which comprises aplug-in element which interacts with an accommodating opening formed ina housing wall. This plug-in element has at least two plug-in sections,which are formed so as to be offset in the plug-in and axial direction,which have different diameters and which are separated from one anotherin the axial direction by means of a circumferential groove. The plug-insection having the greater diameter has a knurl on its circumferentialsurface. For the purpose of producing the electrical connection, theplug-in element is pressed into the corresponding accommodating openingin the housing wall. During the pressing-in operation, the material ofthe housing wall is pressed into the groove of the plug-in element,which results in the plug-in element being fixed axially in the housingwall. In addition, the knurl is forced into the housing wall, whichmakes it possible to fix the plug-in element such that it is securedagainst rotation in the housing wall.

Finally, EP 1 087 466 A2 discloses a sleeve-like terminal connectorhaving a plug-in element which interacts with an accommodating openingwhich is introduced into a housing wall. The plug-in element likewisehas a knurl there on its circumferential surface.

Merely for reasons of completeness, mention is also made of the factthat naturally outer conductors of flexible coaxial cables, for example,can also be electrically connected to a housing by means of soldering.In principle, it is thus possible to produce a good electricalconnection. However, consideration should be made of the fact thatsurfaces of cast housings cannot be soldered. It would first benecessary for the castings to be galvanized. This would lead, on the onehand, however, to considerable excess expense. Secondly, problems withquality owing to complex contours and uniform layer thicknesses wouldresult. In addition, large quantities of heat would be required onsoldering, which would lead to high thermal stresses on the housing andthe cable.

If the mentioned electrical connection devices are provided in anelectromagnetic field (for example an antenna), additional problemsresult which have hitherto been unknown. This is because, in this case,not only the current flow which can always be fixed on the inner side ofthe coaxial cable outer conductor is provided but, owing to theelectromagnetic field, there is also a current flow on the outer side ofthe outer conductor.

If one of the abovementioned electrical connection devices which areknown from the prior art is now chosen, this results in the currentflowing on the inner side of the outer conductor being able to flow in adefined manner towards the inner side of the coupling element, but thecurrent flowing on the outer side of the outer conductor not being ableto flow towards the outer side of the coupling element. Owing tomechanical or thermal stresses, vibrations and jigging phenomena, thecontact conditions are altered and interference signals occur.

It is therefore the object of the present invention to provide animproved electrical terminal connection, in the case of which electricalcontact conditions, which are clearly defined and which can always beclearly reproduced, can be produced both between the inner side of thecoaxial cable outer conductor and housing and between the outer side ofthe coaxial cable outer conductor and housing, to be precise inparticular even when the electrical terminal connection is located in anelectrical field.

The object is achieved according to the invention according to thefeatures specified in claim 1.

Advantageous refinements of the invention are specified in thesubclaims.

The improved electrical terminal connection is characterized by the factthat both the plug-in connection element, which is sometimes alsoreferred to below as the plug-in element 1, and the associated couplingelement, which is sometimes also referred to below as the accommodatingopening, and into which the plug-in element can be inserted, aredesigned to have at least two stages in the axial plug-in direction. Theplug-in element has, when viewed in the plug-in direction, a firstplug-in section and, adjoining it in the axial direction (preferablylying at a spacing offset from said plug-in section), at least onesecond plug-in section which has a radially larger transverse extentthan the first radial plug-in section, at least in partialcircumferential regions. The coupling device is likewise designed tohave two stages and to interact with it. In this case, the plug-insections of the plug-in element are provided on their outercircumference with corresponding engaging elevations, i.e. a form ofknurl, which has a radial or outer or distance dimension, before theplug-in connection is produced, which is at least slightly larger thanthe corresponding dimensions of the accommodating opening. When one partis pressed inside the other, an inner and an outer engagement zone isthus formed, namely an inner engagement zone with the interaction of theplug-in section, which has smaller dimensions, which leads in theplug-in direction and which interacts with a first and/or more inwardlylying and at least with a correspondingly matched coupling openinghaving slightly smaller dimensions, the plug-in section, which haslarger dimensions and which lags in the plug-in direction, interactingwith a section, which has correspondingly slightly larger dimensions, inthe accommodating opening (coupling device). The inner press-in zoneproduces optimum contact between the outer conductor inner side and thecoupling inner side, which may, for example, at the same time alsorepresent the inner side of a housing part or a housing. The outerpress-in zone produces optimum contact between the outer conductor outerside and the coupling outer side, i.e. likewise, for example, again ahousing outer side. As a result, in contrast to the prior art, two clearand optimal electrical contact connections are always realized betweenthe plug-in device and the coupling device, i.e. between the plug-inelement and the accommodating opening.

In this case, a sleeve-like plug-in element is preferably used which ismade of a material which is harder than the material of the couplingdevice, i.e., for example, the material of a plate, wall, housing wallor generally of a housing etc. with which contact is to be made and intowhich the accommodating opening is introduced for the purpose ofaccommodating the plug-in element. However, it is preferably intendedfor the material of the sleeve-like plug-in element to have the same, orat least a similar, coefficient of thermal expansion as the material ofthe coupling device.

An axial knurl or a transverse knurl is preferably provided. The knurlteeth can in this case be formed with tips, in which case they arepreferably provided with insertion slopes at their leading end. Theseinsertion slopes serve the purpose of preventing chipping during thepress connection procedure.

The overall mode of operation is preferably such that the knurl tips ofthe plug-in connection element make notches in the housing material ofthe coupling element, which interacts with said plug-in connectionelement and which is generally in the form of a socket. As a result,there is elastic and plastic deformation of the corresponding material.In turn, this results in an excellent force-fitting connection. Owing tothe elastic deformation component, the explained connection can thusalso be used in the case of thermal cycling, and it is not necessary toform an interlocking connection of the plug-in element such that it isfixed in position.

The entire system can preferably be adapted such that both outer knurlsat the same time make contact with corresponding material holes in thecoupling device. This makes it easier to center and align the sleeveprior to pressing-in.

In principle, it is also possible for the system to be adapted suchthat, for example, initially the leading press-in section of theelectrical plug-in connection elements comes into contact with thecorresponding accommodating section in the coupling element and then,only after an albeit small axial press-in movement of the lagging secondpress-in section, comes into contact with the outer accommodatingsection, having larger dimensions, of the coupling device, or viceversa.

In principle, it is in addition also possible for the correspondingknurls to be provided on the inner surfaces of the coupling elementwhich then interacts with possibly smooth outer circumferential surfaceson the at least two-stage plug-in element.

The defined contact situations which are markedly improved in accordancewith the invention both in the inner and in the outer plug-in connectionregion result owing to the fact that the number of contacts is the sameas the number of knurl tips. The contacts are preferably evenlydistributed over the circumference. Furthermore, gas-tight, metallic endcontacts can be realized, since oxide layers are destroyed by thesliding movement when pressing-in and, at the same time, a self-cleaningprocess also takes place.

In one development of the invention, provision may be made for thesection acting as the stop to hit against a correspondingly shaped stopsection in the coupling device, which is in the interior of the couplingdevice, between the leading plug-in section having smaller dimensionsand the lagging plug-in section which is provided with a largerdiameter. If the coupling device is, for example, formed in anelectrically conductive housing wall, the inner stop lies in the -innersection of the housing wall. This results in optimum assemblyconditions, since the pressing-in procedure can be ended simply by meansof force limitation. Finally, as a result even higher bending stressesof the preferably sleeve-like plug-in connection elements are possible.Owing to the stop limitation realized in the interior of the coupling,it is also not possible for any dust particles to penetrate the housingor the coupling device.

Owing to this formation, it is also possible for the diameter of apressing-in die used to have the same dimensions or even to have smallerdimensions than the diameter of the preferably sleeve-like plug-inconnection device. This is because the axial advance movement is limitedby the mentioned stepped stop. This ensures that the coupling device orthe housing is not partially pressed in during the pressing-in procedureand that impressions of the die are not visible after the assemblyprocess.

Finally, the axial length of the preferably sleeve-like plug-in element,which is also sometimes referred to below as the plug-in connectionelement, is dimensioned such that the height of the press-in sectioncorresponds to the height or the axial physical length of the couplingdevice, which is advantageous in particular when the coupling device ispart of a plate or housing wall with which contact is to be made. Sincehigh-frequency alternating currents flow on the surface of conductorsowing to the skin effect, optimum current flow towards the inner sideand the outer side of the housing wall or the like, which is providedwith the accommodating opening, is thus realized.

It has also proved to be favorable if at least a small circumferentialgroove is provided between the two press-in sections on the electricalplug-in connection element. This makes it possible, for example, for theknurl structure to be cut cleanly into the outer circumferential regionsof the two press-in sections. This also makes it possible to produce aclearly defined, stepped stop surface between the press-in sections.

Finally, it is also possible for a protrusion to be formed over thepress-in section of the plug-in element which has larger dimensions,said protrusion preventing solder from being able to flow onto the twopress surfaces when the cable is connected to the preferably sleeve-likeplug-in connection device by means of soldering.

Naturally, the sleeve-like plug-in element may be soldered to the outerconductor of a coaxial cable before it is pressed into the couplingdevice. However, it is likewise also possible for there to be apressing-in procedure into the coupling device in order in this casethen to solder the electrical conductor, in particular the outerconductor of a coaxial cable, in a second step.

The multi-stage connection device according to the invention mayparticularly advantageously be used if the coupling element is intendedto be produced by means of casting and if it needs to be provided withbeveled deformations.

The invention will be explained in more detail below with reference toexemplary embodiments. In the drawing:

FIG. 1: shows a schematic cross-sectional illustration through a firstexemplary embodiment according to the invention having a sleeve-likeplug-in element (positioned on a section of an outer conductor of acoaxial cable from which the insulation has been stripped) and anaccommodating opening (coupling device) formed in a housing wall priorto the press connection;

FIG. 2: shows a schematic perspective illustration of a preferredembodiment of a sleeve-like plug-in element;

FIG. 3: shows a corresponding schematic perspective illustration of thesleeve-like plug-in element shown in FIG. 2, but viewed more from therear;

FIG. 4: shows a further perspective illustration, but at a viewing anglemore from the rear compared with that in FIG. 3;

FIG. 5: shows an illustration corresponding to that in FIG. 1 once thepress connection is complete;

FIG. 6: shows a modified exemplary embodiment to that shown in FIG. 5,in the case of which the accommodating opening (coupling device) isformed on a thicker housing section;

FIG. 7: shows an exemplary embodiment, which is modified compared tothat shown in FIGS. 1 to 5, in the case of which the two-stage plug-inelement can be inserted from the opposite side into the accommodatingopening (coupling device) which is formed on the housing wall;

FIG. 8: shows an exemplary embodiment, which is modified compared tothat shown in FIGS. 1 to 5, in the case of which the plug-in elementwith its two-stage press attachment does not have an axial hole passingthrough it for the purpose of accommodating an electrical connectionline, in particular coaxial connection line, but has an accommodatinghole, which extends perpendicular thereto, in an accommodating section;

FIG. 9: shows an illustration corresponding to that in FIG. 8, but morein the direction of the front side of the sleeve-like plug-in element;

FIG. 10: shows a perspective illustration of a modified exemplaryembodiment having a more rectangular basic shape; and

FIG. 11: shows a corresponding illustration to that in FIG. 10 with aperspective view, but viewed more from the rear.

A first exemplary embodiment will be explained below with reference toFIGS. 1 to 5.

FIG. 1 shows a schematic cross section of a coaxial terminal connection,which comprises, firstly, a plug-in element 1 and, secondly, a couplingdevice 3, which in the exemplary embodiment shown is in the form of atwo-stage hole in a wall 7, i.e. an electrically conductive housing wall7 or a wall 7 forming part of a housing.

The plug-in element 1 is in this case in the form of a sleeve and has anactual plug-in insert 111, which comprises a leading plug-in section 111a and a second plug-in section 111 b which lags in the plug-indirection. The two plug-in sections 111 a and 111 b are provided suchthat they are offset with respect to one another in the plug-indirection, i.e. in the axial direction, by the width of an annulargroove 111 c. The annular groove 111 c in this case has a smallerdiameter than the two outer diameters of the plug-in inserts 111 a and111 b.

The illustration shown in FIGS. 1 to 5 shows the fact that the plug-inelement 1 is formed with a sleeve attachment 111 d, which is formed suchthat it extends axially, on the side 1 a which is at the rear withrespect to the plug-in direction.

The plug-in element 1 has an inner hole 17, which is at least slightlylarger than the outer diameter of an outer conductor 19 a, from whichthe insulation has been stripped, of a coaxial cable 19. The axiallength of the inner hole 17 almost passes through the entire axiallength of the plug-in element 1, except for a stop shoulder 21 having ahole 23 having a slightly smaller diameter than the inner hole 17. Thisstop shoulder 21 having the annular attachment 21 a formed thereby isthus formed on the end side 1 b which lies at the front in the plug-indirection. As a result, the coaxial cable 19, from which the insulationhas been stripped away down to the outer conductor 19 a, can be insertedinto the plug-in element 1 until it stops against the stop shoulder 21.Before the further connection to the accommodating opening 3 or elseafter the connection to the coupling device 3 has been produced, asoldering procedure can then be carried out in order to effectivelyelectrically conductively connect the outer conductor 19 a to theelectrically conductive plug-in element 1 by means of the solder 25. Thecorresponding inner conductor 19 b finally passes through the plug-inelement 1 at a suitable length, as is illustrated, for example, inFIG. 1. In this case, it can also be seen from the drawings that thehole 23 is dimensioned such that the inner conductor 19 b of the coaxialcable 19 can be passed through it without any problems and plugged in,without, in the finally positioned state of the inner conductor,electrical contact being made with the plug-in element 3.

As can be seen in FIGS. 2 to 4, the plug-in section 111 a lying at thefront in the plug-in direction has a smaller outer diameter than thesecond plug-in section 111 b which lags in the plug-in direction. Thetwo plug-in sections are provided on their outer circumference with aknurl 27, for example an axial knurl or a transverse knurl etc., whoseouter diameter, before the connection to the coupling device 3, is atleast slightly larger than the corresponding inner diameter of thecoupling device 3 which is yet to be explained below.

As can be seen in FIG. 1 with reference to the exemplary embodiment, thecoupling device 3, which is in this case incorporated in the form of anelectrical housing wall 7, is likewise of two-stage design and has afirst accommodating section 211 a having a smaller diameter and a secondaccommodating section 211 b, which lies offset with respect thereto inthe axial direction, having a larger diameter. The two diameters or thetwo shapes and sizes of the accommodating plug-in sections 211 a and 211b are matched in principle to the shape and size of the two plug-insections 111 a and 111 b, which are likewise offset, and differ only inthe fact that the outer circumference on the plug-in attachments isslightly larger than the respectively associated accommodating sections211 a and 211 b owing to the knurl 27 which is introduced at saidplug-in attachments before they are inserted into the accommodatingopening 3 (coupling device). The core diameters of the plug-in sectionsprovided with a knurl are, however, smaller than the corresponding innerdiameters of the accommodating opening 3, with the result that afterpressing-in, contact is only made with the knurl tips, and only lowjoining forces are required even in the case of very large dimensions.Owing to the introduction of the circumferential annular groove 111 c,advantages in terms of manufacturing result when the knurl 27 formed onthe outer circumference is produced. In the lead direction, in this casethe respective knurl 27 is in each case provided with a flattenedsection 29 in order to prevent chipping during assembly. The surface 31,which points towards the front in the plug-in direction, of the plug-insection 111 b having larger dimensions in this case at the same timeacts as a stop surface or stop shoulder 31, which is formed on acorresponding stop surface or stop shoulder 33 at the transition fromthe accommodating section 211 a having smaller dimensions to theaccommodating section 211 b having larger dimensions of theaccommodating opening 3.

In order to produce the fixed connection, the plug-in element 1 is thenpressed into the accommodating opening 3, which is sometimes alsoreferred to as the coupling element 3, by means of a suitable pressingtool (which may have smaller dimensions than the diameter of the plug-insection 111 b having larger dimensions), the outwardly protruding teethof the knurls 27 now forming notches in the material of the housing wall7. Owing to the sliding movement, possible oxide layers are destroyed,and a self-cleaning effect takes place which ensures optimalcontact-making without electrical faults.

The two-stage contact mechanism ensures that currents can flow back andforth both from the inner and from the outer side of the coaxial cableouter conductor (in particular if it is located in an electromagneticfield) in a clearly defined manner to the housing wall 7, that is to sayboth via the contact region A between the leading plug-in section 111 ain interaction with the accommodating section 211 a and also via thefurther interaction in the contact region B between the second plug-insection 111 b which is formed such that it lags in the plug-in directionand the accommodating section 211 b.

The in each case uniquely defined electrical contact zones areidentified by A and B in FIG. 5.

Naturally, a plurality of inner holes 17 may also be provided on theplug-in element 1 for the purpose of accommodating coaxial cables.

The exemplary embodiment shown in FIG. 6 differs from the previousexemplary embodiment only by the fact that the wall section 7 isprovided with a thicker section of material 7′ in the region of theaccommodating opening 3 compared with the remaining housing or wallsections 7.

With reference to exemplary embodiment 7, it is merely shown that thearrangement of the axially offset plug-in sections 111 a and 111 b andthe associated accommodating sections 211 a and 211 b of theaccommodating opening 3 may also be formed in the opposite fashion tothat shown in the exemplary embodiment shown in FIGS. 1 and 5. In theexemplary embodiment shown in FIG. 7, the plug-in element 1 isintroduced into the corresponding recess from the inner side of thehousing. In this case, the soldered connections between the plug-inelement 1 and the coaxial cable can be produced once the pressconnection between the plug-in element 1 and the coupling device 3 hasbeen produced or even beforehand. In this case, the cable needs to bepassed through the coupling opening 211 before pressing-in.

In the exemplary embodiment shown in FIG. 8, it is shown that theplug-in element 1 does not need to be in the form of a sleeve but thatthe corresponding inner hole 17 can also be formed transversely withrespect to the axial direction of the plug-in attachments 111 a and 111b in a rear section 111 f of the plug-in element 1 so as to form a stopshoulder 21. It is also possible for knurls to be provided at both endsof the plug-in element, and for contact to be made with said plug-inelement and, at the same time, two parallel housing walls.

With reference to FIGS. 10 and 11, it is also shown that the plug-inelement 1 does not necessarily need to approximate a circular shape inthe axial view. Elliptical shapes, rectangular shapes or generallyn-polygonal or other basic shapes are also conceivable. In this case,the accommodating sections 211 a and 211 b of the coupling device 3would also have to have a corresponding shape. In this embodiment too,it is the case that the circumferential contour or cross-sectionalsurface, viewed in the axial or plug-in direction, or thecross-sectional size of the plug-in attachment 111 a, which leads in theplug-in direction, is preferably overall smaller than thecross-sectional sizes of the second plug-in attachment 111 b, which lagsin the plug-in direction. Under certain circumstances, it would also besufficient, however, for the leading plug-in section 111 a to havesmaller dimensions than the lagging plug-in section 111 b, at least in across-sectional extent. In addition, the cross-sectional shapes of thetwo plug-in sections may be different, for example the leading plug-insection may be of rectangular design, cf. FIG. 10, whereas the laggingplug-in section having larger dimensions again has more of a circularcross-sectional shape, for example.

For reasons of completeness, mention will also be made of the fact thatthe mentioned knurls 27 do not necessarily need to be formed on theouter circumference of the two plug-in sections, but, quite the reverse,may also be formed on the inner wall, interacting therewith, of the twoaccommodating sections 211 a and 211 b or, alternately, on the outercircumference of one plug-in section and on the inner surface of asecond accommodating section, which is offset with respect thereto, ofthe coupling device.

It can also be seen in the drawings that the respective axial height ofthe plug-in sections corresponds to the axial heights of theaccommodating sections of the coupling device. As a result, in each casethe limit surface which leads in the plug-in direction and the outerlimit surface which lags in the plug-in direction are arranged such thatthey are aligned with the inner and outer housing wall sections.

1. An electrical terminal connection, especially for connecting an outerconductor of a coaxial cable, having a plug-in element, which has aplug-in section and a sleeve attachment for the purpose of accommodatingand connecting an electrical conductor, and having an accommodatingopening, which interacts with the plug-in element and is formed in ahousing wall, the plug-in element being pressed into the accommodatingopening for the purpose of making the electrical connection to thehousing wall, wherein the electrical terminal connection is designed tohave two stages, the plug-in element has at least two plug-in sectionswhich are formed such that they are offset in the plug-in and axialdirection, both the plug-in section which leads in the plug-in directionand the plug-in section which lags in the plug-in direction beingprovided with a knurl on their outer circumference, the secondaccommodating opening has a first and a second accommodating sectionwhich lie such that they are offset in the plug-in and axial directionof the plug-in element, and the two plug-in sections and the twoaccommodating sections, complementary thereto, are designed to havediffering cross-sectional sizes, the radial or outer dimension of theplug-in sections, which are provided with the knurl, being slightlygreater than the radial or outer dimension of the accommodating sectionsrespectively interacting therewith.
 2. The terminal connection asclaimed in claim 1, wherein the cross-sectional size of the leadingplug-in section is smaller than the cross-sectional size of the laggingplug-in section, at least in a partial circumferential region andtransverse to the plug-in direction of the plug-in element.
 3. Theterminal connection as claimed in claim 1, wherein the cross-sectionalsize of the leading plug-in section is smaller than the cross-sectionalsize of the lagging plug-in section in the entire circumferential regionand transverse to the plug-in direction of the plug-in element.
 4. Theterminal connection as claimed in claim 2, wherein the firstaccommodating section of the accommodating opening is smaller than theoffset, second accommodating section, at least in a partialcircumferential region corresponding to the partial circumferentialregion of the plug-in section interacting therewith.
 5. The terminalconnection as claimed in claim 3, wherein the first accommodatingsection of the accommodating opening is smaller than the offset, secondaccommodating section in the entire circumferential region correspondingto the circumferential region of the plug-in section interactingtherewith.
 6. The terminal connection as claimed in claim 1, wherein theinner surfaces of the accommodating sections of the accommodatingopening are designed to have no knurls.
 7. The terminal connection asclaimed in claim 1, wherein, of the outer circumferential surfaces of aplug-in section which each interact in pairs and the inner surface ofthe associated accommodating section of the accommodating opening, ineach case only one section is formed with a knurl and the other surfaceinteracting therewith is formed without a knurl.
 8. The terminalconnection as claimed in claim 1, wherein the knurl is in the form of anaxial knurl or in the form of a transverse knurl.
 9. The terminalconnection as claimed in claim 1, wherein the knurl is provided withleading flattened sections in the plug-in direction.
 10. The terminalconnection as claimed in claim 1, wherein a circumferential annulargroove arranged therebetween is provided between the two outercircumferential surfaces of the plug-in sections.
 11. The terminalconnection as claimed in claim 1, wherein the surface, which leads inthe plug-in direction, of the lagging plug-in section of the plug-inelement acts as a stop shoulder which interacts with a correspondingstop surface between the first and second accommodating section of theaccommodating opening.
 12. The terminal connection as claimed in claim1, wherein the entire axial plug-in height of the plug-in attachmentcorresponds to the axial accommodating height of the accommodatingopening such that, once the pressing-in procedure has been carried out,the plug-in insert which has been pressed into the accommodating openingends flush with the housing wall both on the inside and on the outside.13. The terminal connection as claimed in claim 1, wherein thecross-sectional shape of the plug-in sections of the plug-in element andthe accommodating sections, interacting therewith, of the accommodatingopening are circular or n-polygonal.
 14. The terminal connection asclaimed in claim 1, wherein the plug-in element or housing wall providedwith the knurl is made of a harder material than the housing wall orplug-in element interacting therewith.
 15. The terminal connection asclaimed in claim 1, wherein the sleeve attachment of the of plug-inelement is arranged axially, counter to the plug-in direction, on thelagging plug-in section for the purpose of connecting the coaxial cable.16. The terminal connection as claimed in claim 1, wherein the sleeveattachment of the plug-in element is arranged axially, in the plug-indirection, on the leading plug-in section for the purpose of connectingthe coaxial cable.
 17. The terminal connection as claimed in claim 1,wherein a plurality of internal holes are formed on the plug-in elementfor the purpose of accommodating coaxial cable.